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e2780ab1 PL |
1 | /* |
2 | * Squashfs - a compressed read only filesystem for Linux | |
3 | * | |
4 | * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 | |
5 | * Phillip Lougher <phillip@lougher.demon.co.uk> | |
6 | * | |
7 | * This program is free software; you can redistribute it and/or | |
8 | * modify it under the terms of the GNU General Public License | |
9 | * as published by the Free Software Foundation; either version 2, | |
10 | * or (at your option) any later version. | |
11 | * | |
12 | * This program is distributed in the hope that it will be useful, | |
13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
15 | * GNU General Public License for more details. | |
16 | * | |
17 | * You should have received a copy of the GNU General Public License | |
18 | * along with this program; if not, write to the Free Software | |
19 | * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. | |
20 | * | |
21 | * block.c | |
22 | */ | |
23 | ||
24 | /* | |
25 | * This file implements the low-level routines to read and decompress | |
26 | * datablocks and metadata blocks. | |
27 | */ | |
28 | ||
29 | #include <linux/fs.h> | |
30 | #include <linux/vfs.h> | |
31 | #include <linux/slab.h> | |
e2780ab1 PL |
32 | #include <linux/string.h> |
33 | #include <linux/buffer_head.h> | |
e2780ab1 PL |
34 | |
35 | #include "squashfs_fs.h" | |
36 | #include "squashfs_fs_sb.h" | |
37 | #include "squashfs_fs_i.h" | |
38 | #include "squashfs.h" | |
4c0f0bb2 | 39 | #include "decompressor.h" |
e2780ab1 PL |
40 | |
41 | /* | |
42 | * Read the metadata block length, this is stored in the first two | |
43 | * bytes of the metadata block. | |
44 | */ | |
45 | static struct buffer_head *get_block_length(struct super_block *sb, | |
46 | u64 *cur_index, int *offset, int *length) | |
47 | { | |
48 | struct squashfs_sb_info *msblk = sb->s_fs_info; | |
49 | struct buffer_head *bh; | |
50 | ||
51 | bh = sb_bread(sb, *cur_index); | |
52 | if (bh == NULL) | |
53 | return NULL; | |
54 | ||
55 | if (msblk->devblksize - *offset == 1) { | |
56 | *length = (unsigned char) bh->b_data[*offset]; | |
57 | put_bh(bh); | |
58 | bh = sb_bread(sb, ++(*cur_index)); | |
59 | if (bh == NULL) | |
60 | return NULL; | |
61 | *length |= (unsigned char) bh->b_data[0] << 8; | |
62 | *offset = 1; | |
63 | } else { | |
64 | *length = (unsigned char) bh->b_data[*offset] | | |
65 | (unsigned char) bh->b_data[*offset + 1] << 8; | |
66 | *offset += 2; | |
67 | } | |
68 | ||
69 | return bh; | |
70 | } | |
71 | ||
72 | ||
73 | /* | |
74 | * Read and decompress a metadata block or datablock. Length is non-zero | |
75 | * if a datablock is being read (the size is stored elsewhere in the | |
76 | * filesystem), otherwise the length is obtained from the first two bytes of | |
77 | * the metadata block. A bit in the length field indicates if the block | |
78 | * is stored uncompressed in the filesystem (usually because compression | |
79 | * generated a larger block - this does occasionally happen with zlib). | |
80 | */ | |
81 | int squashfs_read_data(struct super_block *sb, void **buffer, u64 index, | |
118e1ef6 | 82 | int length, u64 *next_index, int srclength, int pages) |
e2780ab1 PL |
83 | { |
84 | struct squashfs_sb_info *msblk = sb->s_fs_info; | |
85 | struct buffer_head **bh; | |
86 | int offset = index & ((1 << msblk->devblksize_log2) - 1); | |
87 | u64 cur_index = index >> msblk->devblksize_log2; | |
88 | int bytes, compressed, b = 0, k = 0, page = 0, avail; | |
89 | ||
90 | ||
91 | bh = kcalloc((msblk->block_size >> msblk->devblksize_log2) + 1, | |
92 | sizeof(*bh), GFP_KERNEL); | |
93 | if (bh == NULL) | |
94 | return -ENOMEM; | |
95 | ||
96 | if (length) { | |
97 | /* | |
98 | * Datablock. | |
99 | */ | |
100 | bytes = -offset; | |
101 | compressed = SQUASHFS_COMPRESSED_BLOCK(length); | |
102 | length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length); | |
103 | if (next_index) | |
104 | *next_index = index + length; | |
105 | ||
106 | TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n", | |
107 | index, compressed ? "" : "un", length, srclength); | |
108 | ||
109 | if (length < 0 || length > srclength || | |
110 | (index + length) > msblk->bytes_used) | |
111 | goto read_failure; | |
112 | ||
113 | for (b = 0; bytes < length; b++, cur_index++) { | |
114 | bh[b] = sb_getblk(sb, cur_index); | |
115 | if (bh[b] == NULL) | |
116 | goto block_release; | |
117 | bytes += msblk->devblksize; | |
118 | } | |
119 | ll_rw_block(READ, b, bh); | |
120 | } else { | |
121 | /* | |
122 | * Metadata block. | |
123 | */ | |
124 | if ((index + 2) > msblk->bytes_used) | |
125 | goto read_failure; | |
126 | ||
127 | bh[0] = get_block_length(sb, &cur_index, &offset, &length); | |
128 | if (bh[0] == NULL) | |
129 | goto read_failure; | |
130 | b = 1; | |
131 | ||
132 | bytes = msblk->devblksize - offset; | |
133 | compressed = SQUASHFS_COMPRESSED(length); | |
134 | length = SQUASHFS_COMPRESSED_SIZE(length); | |
135 | if (next_index) | |
136 | *next_index = index + length + 2; | |
137 | ||
138 | TRACE("Block @ 0x%llx, %scompressed size %d\n", index, | |
139 | compressed ? "" : "un", length); | |
140 | ||
141 | if (length < 0 || length > srclength || | |
142 | (index + length) > msblk->bytes_used) | |
143 | goto block_release; | |
144 | ||
145 | for (; bytes < length; b++) { | |
146 | bh[b] = sb_getblk(sb, ++cur_index); | |
147 | if (bh[b] == NULL) | |
148 | goto block_release; | |
149 | bytes += msblk->devblksize; | |
150 | } | |
151 | ll_rw_block(READ, b - 1, bh + 1); | |
152 | } | |
153 | ||
154 | if (compressed) { | |
4c0f0bb2 | 155 | length = squashfs_decompress(msblk, buffer, bh, b, offset, |
e6a6d379 PL |
156 | length, srclength, pages); |
157 | if (length < 0) | |
158 | goto read_failure; | |
e2780ab1 PL |
159 | } else { |
160 | /* | |
161 | * Block is uncompressed. | |
162 | */ | |
163 | int i, in, pg_offset = 0; | |
164 | ||
165 | for (i = 0; i < b; i++) { | |
166 | wait_on_buffer(bh[i]); | |
167 | if (!buffer_uptodate(bh[i])) | |
168 | goto block_release; | |
169 | } | |
170 | ||
171 | for (bytes = length; k < b; k++) { | |
172 | in = min(bytes, msblk->devblksize - offset); | |
173 | bytes -= in; | |
174 | while (in) { | |
175 | if (pg_offset == PAGE_CACHE_SIZE) { | |
176 | page++; | |
177 | pg_offset = 0; | |
178 | } | |
179 | avail = min_t(int, in, PAGE_CACHE_SIZE - | |
180 | pg_offset); | |
181 | memcpy(buffer[page] + pg_offset, | |
182 | bh[k]->b_data + offset, avail); | |
183 | in -= avail; | |
184 | pg_offset += avail; | |
185 | offset += avail; | |
186 | } | |
187 | offset = 0; | |
188 | put_bh(bh[k]); | |
189 | } | |
190 | } | |
191 | ||
192 | kfree(bh); | |
193 | return length; | |
194 | ||
e2780ab1 PL |
195 | block_release: |
196 | for (; k < b; k++) | |
197 | put_bh(bh[k]); | |
198 | ||
199 | read_failure: | |
118e1ef6 PL |
200 | ERROR("squashfs_read_data failed to read block 0x%llx\n", |
201 | (unsigned long long) index); | |
e2780ab1 PL |
202 | kfree(bh); |
203 | return -EIO; | |
204 | } |